Facing agents for molding sand

ABSTRACT

ACENAPTHYLENE, WHEN INCORPORATED INTO FOUNDRY MOLDING SAND, PREVENTS BURN-ON OF THE SAND GRANULES TO THE CASTING SURFACE, AND PROVIDES A SAND HAVING GOD COLLAPSIBILITY AND GOOD RECYCLE LIFE.

United States Patent Ofice Patented Sept. 19, 1972 US. Cl. 106-3825 14Claims ABSTRACT OF THE DISCLOSURE Acenaphthylene, when incoporated intofoundry molding sand, prevents burn-on of the sand granules to thecasting surface, and provides a sand having good collapsibility and goodrecycle life.

This application is a continuation-in-part of co-pending applicationSer. No. 18,715, filed Mar. 11, 1970, now abandoned.

This invention relates to the casting of metals in sand molds and moreparticularly to a facing agent useful in green sand molds for castingmetals, particularly ferrous metals.

Molding sand compositions for the casting of metals generally comprisesand, clay as a binder and water as a plasticizer. Typically, green sandmolding compositions contain 100 parts of sand, 3 to parts clay,especially montmorillonite clays such as southern or western bentonites,and 2.5 to 5 parts water. In addition to these basic components, it haslong been the practice to employ various auxiliary agents to facilitatecasting of metals in sand molds. These agents include binders, facingagents, expansion control agents and the like. These agents may beapplied to the surface of the mold or dispersed throughout the sand,depending upon the particular function.

As used herein, the term facing agent refers to an additive to a foundrymolding sand which inhibits or prevents burning in or burn-on or thefusing of quartz sand grains to the surface of the casting. Prior tothis invention, facing agents generally were dispersed throughout thesand and have been residue products, usually distillation residues, ofthe coal and petroleum industries, such as sea coal, coal tar pitch,petroleum pitch, asphalt, creosote and various tars. The mechanism bywhich they act is not fully understood, but there are two main theories-(1) they produce a reducing atmosphere within the mold and form a gasfilm between the metal and the mold surface and (2) they perform asooting action and coat the surface of the mold with carbon. Regardlessof theory, the known facing agents do produce a very sooty flame whenburned in air. This is not a particularly valuable criterion forselecting a facing agent, however, since many materials, such asbenzene, naphthalene and antracene which produce sooty flames whenburned in air are ineffective or only moderately effective as facingagents. We believe that this partial or total absence of facing actionresults, at least in part, because of insutficient carbon formation anddeposition at the mold surface during casting. That is, these compoundsvolatilize and are driven away from the mold surface before significantsoot formation can occur. Other materials which are less volatile and doform a carbon deposit at the mold face are known, but they too havetheir drawbacks. These materials, such as sea coal, pitch, asphalt andthe like, contain high proportions of elemental or fixed carbon,

7 which upon pyrolysis during casting forms a rigid coke structure atthe mold surface to a depth determined by the mold geometry, the castingconditions and the thermal gradient developed. This structure binds thesand grains together and causes poor collapsibility of the mold aftercasting. Furthermore, molding sands containing these materials arecharacterized by low recycle life. That is, the facing agent must bereplenished frequently to allow reuse of the molding sand.

It is an object of this invention to provide a novel fac- 7 ing agent.

A further object of this invention is to provide a faC- ing agent whichhas improved efiiciency in preventing burn-on.

Still another object is to provide a facing agent which does not impairthe collapsibility of the mold after castmg.

Another object of this invention is to provide a facing agent having along recycle life.

These and other objects of this invention, which will be apparent fromthe ensuing specification, are achieved by employing acenaphthylene as afacing agent. Molding sands containing acenaphthylene provide a cleanercasting then is obtained with sands containing previously employedfacing agents, and have improved collapsibility and recycle life.

Without wishing to be bound by theory, it is believed that the improvedfacing action observed with acenaphthylene is due to its ability to forma highly refractory, graphite-like coating on the sand granules at themold face, as opposed to the more amorphous carbon coatings obtainedwith previously used facing agents. Moreover, microscopic examination ofthe sand at the mold surface after a casting cycle reveals that theagent of this invention provides a more uniform coating of the sand,both on individual grains and from grain to grain.

' the mold sand spaced from the mold cavity, Where it condenses, thusconserving it for reuse. This action can be observed by a simple testwhereby a Pyrex test tube is charged with sand, then a thin layer (about/8 to inch) of a mixture of sand and facing agent and finally more sand.The bottom of the tube is heated at about 1800 F. and the top is exposedto ambient temperature, and when the layer including the facing agent isheated to about 1000 F. the tube is cooled and the contents examined.The sand in the top end of the tube will be found to containacenaphthylene, while the sand in the bottom of the tube will be foundto be coated with a graphite-like coating.

The acenaphthylene can be employed in pure form, if desired, but due tothe high cost of pure acenaphthylene, it is preferably employed inadmixture with one or more diluents or solvents. For example, crudemixtures, such as petroleum fractions, containing acenaphthylene may beemployed to good effect in accordance with this invention. To bepractically useful, such fractions should contain at least about weightpercent, and preferably at least about weight percent acenaphthylene.The balance of these fractions ordinarily comprises aromatic compounds,primarily polynuclear aromatic compounds such as naphthalene and alkyl(usually methyl) derivatives thereof, and fluorene and alkyl derivativesthereof, although such fractions may contain small amounts of aliphaticcompounds, alkyl benzenes and indanes and tetralins. Sincealkylnaphthalenes, particularly polyalkylnaphthalenes, and fiuorenesprovide limited facing action, their presence as diluents is desirable.Petroleum fractions containing at least about 70 weight percent, andpreferably at least about 85 weight percent of alkylnaphthalenes,fiuorenes and acenaphthylene are especially preferred.

A commercially-available petroleum fraction which is preferred for usein accordance with the present invention is one sold by Getty Oil Co. asAromatics 500, which contains about 90 Weight percent of the polynucleararomatics acenaphthylene, fiuorenes and alkylnaphthalenes. Thespecification and a typical analysis of this fraction are as follows:

TABLE I Specifica- Spot Tests tions analysis Distillation:

IBP F It is desirable that the facing agent have a low sulfur content,i.e., a sulfur concentration of less than about 1%, since the presenceof undue amounts of sulfur is deleterious to the mechanical propertiesof most ferrous and nonferrous metal castings.

The acenaphthylene may be incorporated into molding sand in any suitablefashion. For example, it may be mixed with the sand, in combination withother additives if desired, and the resulting sand mixture is used toform the mold. Alternatively, the sand mold may be formed and theacenaphthylene applied to the mold face by suitable techniques, as bybrushing or spraying. It has also been found that the acenaphthylene canbe applied to the pattern used in forming the mold, with sufficienttransfer to the mold surface occurring to provide facing action.

When acenaphthylene is mixed with the sand, the amount in which it isemployed is not narrowly critical, provided it is an amount suflicientto provide improved facing action. This amount can vary considerablydepending upon the molding sand, the metal being molded and the moldingtechniques employed. For example, greater amounts of facing agent arerequired when the molding sand has greater clay content, a greater watercontent, and is composed of coarser sand or is composed of a lessrefractory sand, i.e. ,a sand which has an increased glassformingtendency. Increased amounts of facing agent are usually required whencasting iron having a low carbon content, when casting at highertemperatures, or when the casting is allowed to cool longer in the mold.Greater amounts of facing agents are also generally required with largercastings, as well as with molding sands which have been recycled manytimes. Ordinarily, however, the effective amount of acenaphthylene willbe in the range of from about 0.1 weight percent to about 5 weightpercent.

When admixed with the molding sand, the acenaphthylene facing agent canbe added as such or in admixture with other desirable additives forfoundry molding sands. A particularly preferred mold of addition is tofirst admix the facing agent with an expansion control agent and thenadd the combination to the molding sands. Expansion' control agents areknown to the art, and normally comprise cellulosic materials, such aswood flour, starches, cereals and the like. A particularly desirableexpansion control agent is a modified starch as disclosed in U.S. Pat.No. 3,086,874. When employed in such mixtures, the facing agent andexpansion control agent are combined in the proportions in which theyare to be employed in the molding sand, ordinarily from about 0.5 toabout 5 parts by weight of expansion control agent per part of facingagent, and preferably about 2 parts per part of expansion control agentper part of facing agents.

As noted above, .the facing agent of this invention also can be applieddirectly to the mold surface by suitable techniques, such as brushing orspraying. If it is applied as a spray, airless spray techniques shouldbe employed to -ensure efiicicnt deposition of the agent on the moldsurface and avoid overspray or loss of agent due to entrainment in theair stream which may occur with conventional air sprays. The amountapplied to the surface is not narrowly critical, provided the desiredfacing action is obtained. Ordinarily amounts of at least about 0.5 gramper square foot of surface are required to achieve a useful effect, andamounts of from about 1 to about 5 grams per square foot will be mostcommon. Still greater amounts can be used if desired, but generally areunnecessary. It is an advantage of the agent of this invention thatexcessive amounts applied to the surface are not detrimental.

Since pure acenaphthylene is a solid, it must be dissolved in a suitablesolvent for application as a spray. Neither the solvent employed nor theconcentration of the solution is critical to this invention. All that isrequired is that the solvent dissolve the acenaphthylene and notinterfere With its facing action and that the resulting solution containsufficient acenaphthylene to provide adequate facing action at usefulapplication rates and yet not be too viscous for application. Suitablesolvents include aliphatic compounds and fractions such as kerosene andthe like, aromatic compounds such as benzene, toluene and the like, andalcohols such as methanol, ethanol and the like. The concentration ofthe acenaphthylene in the solution can vary from about 1 weight percentto about 20 weight percent.

The following examples are illustrative. In the examples, facing actionwas evaluated by making step castings having a rectangular drag surfacemeasuring four inches by twelve inches. The cope surface was providedwith three steps measuring four inches by four inches, and thethicknesses of the steps were one-half inch, one inch and two inches.Unless otherwise specified, the molding sand employed contained partsAFS fineness number 70 sand, 3 parts southern bentonite (acid), 3 partswestern bentonitc and varying amounts of water and facing agent. Allparts and percentages are by weight, and the amounts of sand componentemployed is based upon 100 parts of the D grade sand.

EXAMPLE 1 Molding sands including 3.5 parts water and 2 parts of eitherthe petroleum fraction identified in Table 1, above, or an aqueous 60%solids asphalt emulsion sold commercially as a facing agent wereprepared by mulling the dry sand and bentonite clays for 2 minutes,adding water and mulling for minutes and adding facing agent and mullingfor 5 to minutes. The molds were made by jolting cope and drag 50 timesand then squeezing at full line pressure (90 p.s.i.). Castings were madeusing gray iron (50% new iron) at 2740 F., and shake-out was after 45minutes. A step casting made with the asphalt facing agent had very poorpeel, whereas the casting made using the petroleum fraction as thefacing agent had very good peel, even on the drag surface, and flakegraphite was observed on all surfaces.

Additional runs were performed to determine whether the poorer resultsobtained with the asphalt emulsion were due to the higher total watercontent (4.3 parts) or lower solids (asphalt) content (1.2 parts). Inthe first run, 2.7 parts water and 2 parts emulsion were employed (3.5parts total water and 1.2 parts asphalt solids) and in the second 2.2parts water and 3.4 parts emulsion (3.6 parts total water and 2 partsasphalt solids). Nd difference in casting appearance was observed in thetwo runs using 2 parts of emulsion. In the run using 3.4 parts emulsion(2 parts asphalt), however, an improvement was observed over both theruns using 2 parts asphalt emulsion in that good peel was observed inthe cope of the light section. Nevertheless, poor peel was observed onthe intermediate section and a partial peel on the heavy section and thedrag and sides were poor.

EXAMPLE 2 A molding sand including 3.5 parts water and 2 parts of thepetroleum fraction identified in Table I was prepared by mulling the drycomponents for 2 minutes, adding the water and mulling for 5 minutes,and adding the petroleum fraction and mulling for 10 minutes. The moldwas prepared and step castings were made as described in Example 1. The2-ram cores came out after 3 to 4 drops. The peel of the castings wasexcellent.

The sand was recovered, mulled for 2 minutes with 0.25 part each ofsouthern bentonite (acid) was western bentonite, and then 5 minutes with3.5 parts water, and the casting procedure was repeated. The cores shakeout with 2 drops. Again excellent peel was observed, even in the drag.

Four additional cycles, during which only 0.25 part of each of thebentonite clays was added in each cycle, were carried out. Excellentpeel was observed on the first two cycles, some burn-on (no worse thanthat observed with commercially available facing agents) was observed onthe third, and burn-on was noted on the heavy section after the fourthcycle.

The recycle test was repeated, this time using a 60% solids asphaltemulsion used commercially as a facing agent. The dry sand ingredientswere mulled for 2 minutes, then 5 minutes with 2.14 parts water, andthen 10 minutes with 3.4 parts of the emulsion (for a total of 3.5 partswater and 2 parts asphalt solids). The cores came out with 5 drops. Thecasting evidenced heavy burnon in the drag, although the cope sectionswere good.

The sand was recovered, mulled for 2 minutes with 0.25 part each ofsouthern bentonite (acid) and western bentonite and 5 minutes with 3.5parts water and step castings were made. The cores came out with 6 to 7drops. The entire surface of the drag of the casting was covered withsand, and although the cope was generally good, some sand adhered to thecope sections.

The retempering and molding procedures were repeated, and the castingswere generally poor, with burnon evident in cope and drag.

The results of these tests are summarized in Table II.

TABLE IL-RECYCLE LIFE OF FACING AGENTS Petroleum fraction of Table I 1Asphalt 1 Core Core removed Casting removed, Casting Cycle dropsappearance drops appearance 1 3-4 Excellent- 6 Cope, good, drag, heavyburn-on. 2 2 do 6-7 Burn-on on cope and drag. 3 1 ..do 5-7 Poor, heavyburn-on. 4 1-2 do 5 1 Some burn-on 6 2-3 Burn-on on heavy sections.

1 2 parts per 100 parts sand. 2 3.5 parts 60% aspahlt emulsion (2 partsasphalt) per 100 parts sand.

As is evident from Table II, the petroleum fraction was markedlysuperior to the asphalt as a facing agent, both initially and as torecycle life. Thus, at equivalent solids content in the first cycle, thepetroleum fraction yielded a superior casting, was completely effectivethrough 4 cycles and was of some benefit through 6 cycles, while theasphalt was not fully effective in the first cycle, and its effectrapidly deteriorated to essentially nil in only 3 cycles.

EXAMPLE 3 The petroleum fraction identified in Table I, above, wasblended with wood flour to provide a composition containing 70 partswood flour and 30 parts petroleum fraction. Molding sand was thenprepared by dry mulling the said including 2 parts of this blend for 2minutes and then wet mulling with 3.5 parts water for 10 minutes. A stepcasting was produced as described in Example 1.

The experiment was repeated, except that a commercially available blendof equal parts of wood flour and asphalt was substituted for thepetroleum fraction-wood flour blend.

The casting obtained with both additives were equal in appearance,despite the fact that the petroleum fraction was employed in loweramounts (0.6 part) than the asphalt (1 part).

EXAMPLE 4 Employing procedures and amounts similar to those described inExample 1, except that 1 part of acenaphthylene was employed as thefacing agent, a casting was made with gray iron new, /3 remelt) at 2790F. The casting evidenced no burn-on on the cope faces and the drag hadonly a light burn-on. The cope surface at the heavy section had severalhollows that apepar to be caused by gas. Castings made with the samesand, but with no facing agent, exhibited heavy burn-on in the cope anddrag. Castings made substituting 1 part of the petroleum fraction ofTable I for the acenaphthylene were not quite as clean on the copesurfaces as that first obtained, but were equal in the drag.

EXAMPLE 5 A number of polynuclear aromatic compounds, or mixturesthereof, were subjected to proximate volatile matter tests (ASTM TestD-244 modified only by heating at 900 F. or 1000 F. for 7 minutes) andobserved for formation of a sooty smoke and a graphitic residue in thecrucible. Of all of the materials tested, only acenaphthylene wasobserved to spontaneously ignition with the formation of a sooty smokeand leave a substantial graphitic residue. The results of these testsare summarized as follows:

Two strips of sand, one admixed with 0.5 weight percent acenaphthylene,and the other admixed with 0.5 weight Ignition Ignition and sooty Carbonand sooty Carbon flame PVM 1 Deposit flame PVM Deposit Naph thalcne2-methylnaphthalena. Dimethylnaphtalene. 'Irirnethylnaphthalen BiphenylPhenanthrene Fluorene Acenaphthene Acenaphthylene A 500 Plusdimethylnaphthalene Plus t-rimcthylnaphthalcne Plus fiuorene 9 Yes None.

Yes. Yes. Yes. Yes. Yes.

1 PVM=Proximate Volatile after. 2 A clear brown residue was observed. 3Mixtures of equal parts A 500 and the named compound.

From the foregoing it is apparent that only acenaphthylene orcompositions containing it underwent spontaneous combustion, had asignificant amount of non-volatile matter and left a graphitic residuein the cruicible. Of the materials evaluated which did not contain atleast some acenaphthylene, only crude anthracene evidenced a significantnon-volatile matter content (less than 99 percent), but it did notignite. Moreover, crude anthracene is known to contain a high proportionof fixed carbon, which probably contributed to the carbon deposit, sincepure anthracene left little or no residue. On the other hand,acenaphthene did spontaneously ignite with the formation of a sootyflame, but this material did not leave a carbon resdiue and wasessentialy 100% volatile. Thus, of the materials tested, onlyacenaphthylene and mixtures containing it evidenced both the highsooting activity combined with the ability to deposit in situ asubstanial carbon deposit which is essential to a superior facing agent.

EXAMPLE 6 A %-inch diameter by 6-inch long test tube was charged with amixture of grams of AFS 50-70 sand and 0.5 grams of acenaphthylene, anda second test tube was charged with a mixture of 10 grams of AFS 50-70sand and 0.5 gram of acenaphthene. The two tubes were wired together andthe bottoms were centered in the flame of a Meeker burner so they wereequally heated. The tubes were heated for 10-15 minutes, during whichtime both sands began to darken, beginning at the bottoms of the tubes.With the acenaphthene-containing sample, darkening continued to achocolate brown color, at which point the color began to lighten and, atthe end, the sand became practically the same color as the initial sandsample.

In the case of the acenaphthylene-containing sample, on the other hand,darkening continued until the sample exhibited a shiny, black, coke-likecolor, and at the end. of the test period a strong covering ofcarbonaceous material remained on each sand gram. Analysis of the sandresidues by a loss on ignition test showed that the acenaphthyleneresidue was about 10 times that of the acenaphthene residue. Theacenaphthylene residue had a volatile content in this test of 1.44percent and the acenaphthene residue a volatile content of only 0.11percent.

From this test it can be seen that acenaphthene does not form atenacious carbon deposit on heating whereas acenaphthylene does. Thus,only acenaphthylene can form a carbonaceous deposit at the mold surfaceand thereby afford good facing action.

EXAMPLE 7 A green sand mold was prepared by conventional procedures forcasting an 8-inch by 8-inch square casting having a step-likeconfiguration, one-half having a /2-iuch thickness and the other halfhaving a 2-inch thickness.

percent acenaphthene, were deposited on the mold floor adjacent the moldwalls. Then gray iron at 2750 F. was poured, and allowed to cool and theresulting casting was shaken out and brushed. The surface of the castingadjacent the acenaphthylene-treated sand had much less sand adhering toit than did the surface adjacent the acenaphthene-treated sand.

On examination of the mold, the acenaphthylenetreated sand was black andwell coated with graphitic carbon to a depth of about one inch, whereasthe acenaphthene-treated sand was a dull, light brown to gray color.Samples of these treated sands were taken to a depth of about /2-inchand subjected to a loss on ignition test. The acenaphthylene-treatedsand was found to contain double the organic residue found with theacenaphthene-treated sand, thus confirming the persistence of theacenaphthylene residues at the mold surface to provide facing action.

EXAMPLE 8 A 6-cavity mold (each cavity having the shape of a 3 /2-inchsquare Z-Stepped block having a /s-inch thick step and a l /z-inch thickstep) was formed from a molding sand composed of parts by weight 60 AFSsand, 4 parts by weight western bentonite, 4 parts by weight southernbentonite and 4.3 parts by weight water. Employing an air-less spraygun, a solution of equal parts by weight of the fraction identified inTable I and kerosene was applied to the mold cavities at a rate of Agram of solution per second. The length of the application varied foreach cavity as follows: 1, 2, 4, 8, l6 and 32 seconds. Thereafter a testcasting was made and the sample was examined for facing action. -It wasfound that a 2-second spray time -(or /2 gram per 30 square inches ofsurface) was required for effective facing action at the inch section,and a spray time of 8 seconds (or 2 grams per 30 square inches ofsurface area) was required for effective facing action at the 1 /2 inchstep.

EXAMPLE 9 A 15 inch by 13 inch pattern plate was sprayed with a solutionof equal parts by weight of the composition identified in Table I andVarsol, a kerosene-like material, at a rate of /2 gram per second for 2seconds. The pattern was then used to form a mold of 100 parts by weightof sand, 6 parts by weight of western bentonite and 3 /2 parts by weightwater, during which the solution was transferred from the pattern to themold sand. A casting which was poured in gray iron using the resultingmold was found to be totally and completely free of sand adhesion, andhad a smooth and shiny appearance. Examination of the sand revealeddeposition of carbon 0n the sand grains to a depth of from about A toabout one inch.

In addition to the facing action it was found that the agent providedgood parting or release agent properties and prevented adhesion of thesand to the pattern. In addition, the mold surface was greatly improved.Apparently the agent reduces the interface friction between the sand andthe pattern and thus permits better compaction of the sand granules atthe mold face surface.

It has been found that transfer of the solution from the pattern to themold face is substantially complete. Thus the solution is ordinarilyapplied to the surface of the pattern at or slightly above the ratenecessary to pro vide facing action if applied directly to the moldface. As a general rule of thumb, however, it has been found sufficientto apply enough solution to the pattern so that it appears wet.

If desired the solution can include other ingredients, such as diluentsand the like. In those instances in which the pattern has large verticalsurfaces, it is desirable to incorporate a thixotroping agent, such asamorphous silica, into the solution.

What is claimed is:

1. In a method for forming a green sand mold for casting metalscomprising forming a green sand mixture of sand, clay and water intosaid mold, the improvement of incorporating acenaphthylene into saidgreen sand mixture at least at the surface of said mold in an amountsufiicient to provide effective facing action during subsequent casting.

2. A method according to claim 1 wherein said acenaphthylene is admixedwith said sand, clay and water before forming said mold.

3. A method according to claim 2 wherein the amount of acenaphthylene isfrom about 0.1 to about 5 weight percent, based upon the weight of sand.

4. A method according to claim 2 wherein said acenaphthylene is in theform of a petroleum fraction containing at least about 70 weight percentof polynuclear aromatic compounds of the class consisting of naphthaleneand methyl derivatives thereof, fiuorene and methyl derivatives thereof,and acenaphthylene, there being at least about weight percent ofacenaphthylene in said fraction.

5. A method according to claim 1 wherein said acenaphthylene is appliedto the mold surface after formation.

6. A method according to claim 5 wherein the amount of acenaphthylene isfrom about 0.1 to about 5 weight percent, based upon the weight of sand.

7. A method according to claim 5 wherein said acenaphthylene is in theform of a petroleum fraction containing at least about 70 weight percentof polynuclear aromatic compounds of the class consisting of naphthaleneand 10 methyl derivatives thereof, fluorene and methyl derivativesthereof, and acenaphthylene, there being at least about 20 weightpercent of acenaphthylene in said fraction.

8. A method according to claim 5 wherein said ace naphthylene is sprayedonto said surface in solution in as solvent therefor.

9. A method according to claim 5 wherein said acenaphthylene is appliedto the surface of the pattern employed in forming said mold, wherebyacenaphthylene is transferred from said pattern to said mold face duringformation of said mold.

10. In a molding sand composition comprising sand, clay as a binder andwater as a plasticizer, the improve ment of acenaphthylene in an amountsufficient to provide effective facing action to a mold made from saidcomposition.

11. A composition according to claim 10 wherein said facing agent ispresent in an amount of from about 0.1 to about 5 weight percent, basedupon the sand.

12. A composition according to claim 10 wherein said acenaphthylene isin a petroleum fraction containing at least about weight percentpolynuclear aromatic compounds of the class consisting of naphthaleneand methyl derivatives thereof, fiuorene and methyl derivatives thereofand acenaphthylene, there being at least about 20 weigth percentacenaphthylene in said fraction.

13. A composition useful as an additive to molding sand including fromabout 1 to about 5 parts by weight of a cellulosic expansion controlagent and about 1 part by weight of acenaphthylene.

14. A composition according to claim 13 wherein said acenaphthylene isin the form of a petroleum fraction containing at least about 70 weightpercent by polynuclear aromatic compounds of the class consisting ofnaphthalene and methyl derivatives thereof, fluorene and methylderivatives thereof, and acenaphthylene, there being at least about 20weight percent of acenaphthylene in said fraction.

References Cited UNITED STATES PATENTS 2,476,933 7/1949 Wallace 106-38252,668,774 2/1954 Heyl 10638.25 3,241,984 3/1966 King et al. 10638.8

LORENZO B. HAYES, Primary Examiner US. Cl. X.R.

UNITED STATES PATENT oTTTcE QERTIFICATE 0F I ECTEQN Patent No. q 6o 550Dated September 19. 1972 Inventor(s) R. E Melcher et a1 It is certifiedthat error appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

Col. 5, line #9, "was" should be --and-.

Col. 6, line ll, "said" should be --sand--.

Col. 6, line 60, "apepar" should be --appear--.

Col. 6, 1ine75, "ignition" should be --ignite--.

Col. 7 in the Table, under "A 500" in the left hand column inse t thefollowing line Naphthalene 3, Yes, 98.16, Yes--; in line2-Methylnaphthalene, under heading PVM (first occurrence) "99.88" shouldread --99.98--; in line Phenanthrene, under heading PVM (firstoccurrence) "99.98"

should read --99.90--; in line Biphenyl, under column Carbon Depositinsert --none--.

Col. 7, line 36, "resdiue" should read --residue--.

Col. 10, line 33, "by" should read ---of---.

Signed and sealed this 20th day of March 1973.

(SEAL) Attest:

EDWARD NLFLETCHERJR. ROBERT GOTTSCHALK Attesting Officer Commissioner ofPatents -'ORM PO-1050 (10-69) USCOMM-DC 6O376-P69 LLS. GOVERNMENTPRINTING OFFICE: I969 0-366-334

